Thank you for providing the link to that tiny quote which you seem to feel is unreasonable. As you know, that was extracted by you more than three-quarters of the way down a very long article that was working through the subject of transubstantiation. To aid others wishing to know what the author said prior to your one-sentence quote, here is the context (and please note that it is his point No. 11):
(11) The Communion elements in the Gospels and 1 Corinthians 11 were
not meant to be understood literally for several reasons:
First, since in the original context, when Jesus said “this is by
body,” everyone present knew it was not literally his real body but a
piece of bread being held by His real body (hand). So, if it is not
understood symbolically, then St. Augustine’s statement is a bold
contradiction when he declared; “Christ bore Himself in His hands,
when he offered His body saying: ‘this is my body’” (Ott,
...Fourth, it was a spiritual participation in Christ’s death with other
believers, not a physical imbibing of it, as Catholics claim. Thus,
Paul said, “the bread that we break, is it not a participation in the
body of Christ?” (1 Cor. 10:16, emphasis added) which was his
spiritual body (see v. 17).
Then comes a summary of the many points which the author feels shows up the error of the transubstantiation doctrine. That one-sentence quote you used is but one in a long list of summary points.
My answer to your question is that the idea of "Jesus holding himself in his own hand" [on the night he instituted that remembrance supper] is fully explained in the article you refer to. Without reading the whole article, that one-sentence quote might well seem unreasonable, especially if one does not know that the author was picking up on St. Augustine's own statement, "“Christ bore Himself in His hands, when he offered His body saying: ‘this is my body’” (Ott, Fundamentals, 377).
But given the development of the author's various arguments, he is making an impactful statement about something St. Augustine said himself, on that matter. See https://normangeisler.com/does-the-nt-support-the-rc-view-of-communion/
When the Bible account is followed, it's obvious that Jesus was using literal bread and literal wine as signs pointing to a still-future sacrifice. Until Christ had actually died and been raised, nobody could participate in consuming elements that actually could be his broken body and shed blood (assuming transubstantiation to be correct). Logically, it would be impossible for Jesus to be holding in his hand a piece of bread that had become his broken, sacrificial body, prior to that body having died in sacrifice.
The second reason is that signs are not the thing they signify. They point TO the thing signified. Christ was holding in his hand a literal piece of bread that was illustrative of what would happen to his body when it was (soon to be) crucified. But until his body actually WAS broken, that piece of bread in Christ's hand could only be a piece of bread.